X-ray tubes and cathodes (e.g., x-ray sources) may be fabricated in many ways, and may serve many purposes. X-ray tubes typically include an electron source, such as a cathode, that releases electrons at high temperatures. Some of the released electrons may impact a target anode. The collision of the electrons with the target anode produces X-rays, which may be used in a variety of medical devices such as computed tomography (CT) imaging systems, X-ray scanners, and so forth. In thermionic cathode systems, a filament including a metal may be used as an electron source. The filament may be induced to release electrons through the thermionic effect, i.e. in response to being heated. However, thermionic X-ray cathode filaments typically may not emit electrons until after being heated to a high temperature at which the material of the filament evaporates, thus reducing its operating life. For flat or planar filaments, this may quickly cause inconsistent electron emission and eventual cathode failure as the filament thins.